One of the things I have always found fascinating is what weeds can tell you about soil health. I think that a great example of this is the way that Ammophila (beach sand dune grass) grows. Why is it there? How does it survive? It’s all very simple in design; Ammophila has an extensive root system that helps keep the sand in place. Because of the amount of drainage in sand, this plant takes in most of its water through the salty air. The salts that are in seawater contain every trace element that is required to grow healthy plants. But aren’t salts bad, you ask? Yes, in high concentrations of organic rich soil, salts bind and dehydrate root zones, which lead to poor plant productivity and hydrophobia. Sand however has no OM to speak of and the salts move freely through the “soil” profile.

Why is this important? Understanding what “invasive” weeds are showing up in your lawns can tell you what is missing. For instance, nitrogen deficiency: a bellwether for soil nitrogen deficiency is any weed that fits into the legume family, like clovers and vetch. These weeds present in a lawn indicate a low presence of soil nitrogen.

Weeds with long tap roots such as dandelion, crabgrass, sedges and the like are indicative of soils that are compacted. These weeds are designed to breakup compacted soil and allow for greater water dispersion. The nice thing about these plants (look on the bright side people) is that when they decompose, their extensive roots will add much needed organic matter and nutrients to the soil. Because they are penetrating deeper soil profiles, these plants have access to nutrients that are typically out of reach for turf.

Dollar weed is a common problem in the tropical zones. Interestingly enough, this weed is from an aquatic family. This can be a great indicator of an area with too much water. You can bet that before long you will be fighting fungus in the same lawn because the soil is not drying out. Another problem you may see is that if Dollar weed is present is a yellowing or malnourished looking lawn. Why? Because the water is taking up too much space in the soil and the roots’ transpiration ability is greatly reduced. Just think of an interstate at rush hour, the road hasn’t changed, but there’s no way you will be getting through it quickly.

Most people think that weeds are competitive for the nutrients that are being applied to their respective crops/turf when, in fact, the opposite is true. In most cases, weeds are only growing because of a lack of soil health. They are there to help balance the system, drain soil, bring nutrients to the surface, add much needed carbon and hold soil in its place.

The next time you look at a lawn and its weed problems, keep this information in mind. There is a reason for its existence and normally it is there because fertility is low. Remember, don’t kill it until you are adding in what that particular plant is contributing. Your business will get a whole lot easier.

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